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智能合约安全指南 🛡️

1. 安全基础

1.1 常见漏洞类型

1. 重入攻击
2. 整数溢出
3. 权限控制缺陷
4. 随机数漏洞
5. 前后运行攻击
6. 签名重放

1.2 安全开发原则

1. 最小权限原则
2. 检查-生效-交互模式
3. 状态机安全
4. 失败保护机制

2. 重入攻击防护

2.1 基本防护模式

contract ReentrancyGuarded {bool private locked;modifier noReentrant() {require(!locked, "Reentrant call");locked = true;_;locked = false;}function withdraw() external noReentrant {uint256 amount = balances[msg.sender];require(amount > 0, "No balance");balances[msg.sender] = 0; // 先更新状态(bool success, ) = msg.sender.call{value: amount}("");require(success, "Transfer failed");}
}

2.2 检查-生效-交互模式

contract CEIPattern {mapping(address => uint256) private balances;function deposit() external payable {balances[msg.sender] += msg.value;}function withdraw(uint256 amount) external {// 检查require(balances[msg.sender] >= amount, "Insufficient balance");// 生效balances[msg.sender] -= amount;// 交互(bool success, ) = msg.sender.call{value: amount}("");require(success, "Transfer failed");}
}

3. 访问控制

3.1 角色管理

contract RoleBasedAccess {using EnumerableSet for EnumerableSet.AddressSet;mapping(bytes32 => EnumerableSet.AddressSet) private roles;event RoleGranted(bytes32 indexed role, address indexed account);event RoleRevoked(bytes32 indexed role, address indexed account);modifier onlyRole(bytes32 role) {require(hasRole(role, msg.sender), "Unauthorized");_;}function hasRole(bytes32 role,address account) public view returns (bool) {return roles[role].contains(account);}function grantRole(bytes32 role,address account) external onlyRole(DEFAULT_ADMIN_ROLE) {if (roles[role].add(account)) {emit RoleGranted(role, account);}}function revokeRole(bytes32 role,address account) external onlyRole(DEFAULT_ADMIN_ROLE) {if (roles[role].remove(account)) {emit RoleRevoked(role, account);}}
}

3.2 权限代理

contract DelegatedAccess {mapping(address => mapping(address => bool)) private delegates;event DelegateChanged(address indexed delegator,address indexed delegatee,bool status);function setDelegate(address delegatee, bool status) external {delegates[msg.sender][delegatee] = status;emit DelegateChanged(msg.sender, delegatee, status);}function isDelegate(address delegator,address delegatee) public view returns (bool) {return delegates[delegator][delegatee];}modifier onlyDelegateOrOwner(address owner) {require(msg.sender == owner || isDelegate(owner, msg.sender),"Not authorized");_;}
}

4. 数据验证

4.1 输入验证

contract InputValidation {uint256 public constant MAX_ARRAY_LENGTH = 100;uint256 public constant MAX_VALUE = 1e20;function validateArrayInput(uint256[] calldata data) internal pure {require(data.length > 0, "Empty array");require(data.length <= MAX_ARRAY_LENGTH, "Array too long");for (uint i = 0; i < data.length; i++) {require(data[i] <= MAX_VALUE, "Value too large");if (i > 0) {require(data[i] >= data[i-1], "Not sorted");}}}function validateAddress(address addr) internal pure {require(addr != address(0), "Zero address");require(addr.code.length == 0, "Contract address not allowed");}
}

4.2 状态验证

contract StateValidation {enum State { Inactive, Active, Paused, Ended }State public currentState;modifier inState(State requiredState) {require(currentState == requiredState, "Invalid state");_;}function validateTransition(State newState) internal view {if (currentState == State.Inactive) {require(newState == State.Active, "Invalid transition");} else if (currentState == State.Active) {require(newState == State.Paused || newState == State.Ended,"Invalid transition");}}
}

5. 签名验证

5.1 EIP712 签名

contract EIP712Verifier {bytes32 private DOMAIN_SEPARATOR;struct EIP712Domain {string name;string version;uint256 chainId;address verifyingContract;}constructor(string memory name, string memory version) {DOMAIN_SEPARATOR = keccak256(abi.encode(keccak256("EIP712Domain(string name,string version,uint256 chainId,address verifyingContract)"),keccak256(bytes(name)),keccak256(bytes(version)),block.chainid,address(this)));}function verifySignature(bytes32 hash,bytes memory signature) internal view returns (address) {bytes32 digest = keccak256(abi.encodePacked("\x19\x01", DOMAIN_SEPARATOR, hash));return ecrecover(digest, signature[0], signature[1], signature[2]);}
}

5.2 签名重放防护

contract ReplayProtection {mapping(bytes32 => bool) private usedSignatures;function isSignatureUsed(bytes32 hash) public view returns (bool) {return usedSignatures[hash];}function markSignatureAsUsed(bytes32 hash) internal {require(!usedSignatures[hash], "Signature already used");usedSignatures[hash] = true;}function validateSignature(bytes32 hash,bytes memory signature,uint256 deadline) internal view returns (address) {require(block.timestamp <= deadline, "Signature expired");require(!isSignatureUsed(hash), "Signature already used");return verifySignature(hash, signature);}
}

6. 紧急响应

6.1 紧急停止

contract EmergencyStop {bool public stopped;address public guardian;modifier whenNotStopped() {require(!stopped, "Contract is stopped");_;}modifier whenStopped() {require(stopped, "Contract is not stopped");_;}function toggleStop() external {require(msg.sender == guardian, "Not authorized");stopped = !stopped;emit EmergencyToggled(stopped);}function emergencyWithdraw() external whenStopped {require(msg.sender == guardian, "Not authorized");// 执行紧急提款逻辑}
}

6.2 漏洞修复

contract UpgradeableSecurityFix {address public implementation;address public admin;function upgrade(address newImplementation) external {require(msg.sender == admin, "Not authorized");require(newImplementation.code.length > 0, "Not a contract");// 验证新实现是否兼容require(IUpgradeable(newImplementation).supportsInterface(0x01ffc9a7),"Incompatible implementation");implementation = newImplementation;emit Upgraded(newImplementation);}
}

7. 审计和测试

7.1 自动化测试

const { expect } = require("chai");
const { ethers } = require("hardhat");describe("SecurityTests", function() {let contract;let owner;let attacker;beforeEach(async function() {const Contract = await ethers.getContractFactory("SecureContract");[owner, attacker] = await ethers.getSigners();contract = await Contract.deploy();});it("Should prevent reentrancy attacks", async function() {await expect(contract.connect(attacker).withdraw()).to.be.revertedWith("Reentrant call");});it("Should validate access control", async function() {await expect(contract.connect(attacker).adminFunction()).to.be.revertedWith("Not authorized");});
});

7.2 形式化验证

/// @notice Invariant: total supply should always equal sum of balances
/// @custom:invariant totalSupply == sum(balances)
contract VerifiedToken {mapping(address => uint256) public balances;uint256 public totalSupply;function transfer(address to, uint256 amount) external {require(balances[msg.sender] >= amount, "Insufficient balance");balances[msg.sender] -= amount;balances[to] += amount;assert(balances[msg.sender] <= totalSupply);assert(balances[to] <= totalSupply);}
}

8. 相关资源

• 智能合约安全最佳实践
• OpenZeppelin 安全博客
• 以太坊安全工具集
• Slither 静态分析工具
• MythX 安全平台